CTB-004 Color Correction Filter
½-CTB glass filter: boosts blue (440 – 500 nm ≥ 80 % T) while smoothly trimming red—lifting 3200 K lamps ≈ 1500–1800 K cooler without heavy loss.
- Blue peaks: 85 % T @ 388 nm • 94 % @ 440 nm • 93 % @ 492 nm
- Wide boost: ≥ 70 % T @ 380 – 513 nm (steady output)
- Red attenuation: ~50 % T @ 525 nm → 20 % T @ 700 nm
- CCT lift: +1500 – 1800 K (≈ ½-CTB)
- Construction: Ion-assisted hard-oxide; 5 – 450 mm, 0.21 – 3.8 mm thick
- Custom options: Bump flattening, AOI tuning, rapid prototypes
Learn more
CTB-004 provides a medium “cool-blue” lift—about a ½-CTB step—ideal when a full CTB film
would steal too much punch. Transmittance rises through three distinct peaks (85 % @ 388 nm, 94 % @ 440 nm,
93 % @ 492 nm) and never drops below 70 % until 513 nm, delivering generous blue-green energy. Past 515 nm the
spectrum rolls away smoothly: ~50 % T at 525 nm, ~33 % at 550 nm, ~20 % at 700 nm, ensuring skin tones stay
natural, not cyan-shifted.
All-oxide coatings survive 1 kW halogen heat or high-power LED engines, and KUPO can cut Borofloat®, soda-lime,
Schott D263 T, or Corning Eagle XG glass to any outline—from 5 mm chips to 450 mm plates—within
0.21 – 3.8 mm thickness. Prototypes ship in ~2 weeks.
Typical uses: subtle CTB on stage/architectural rigs, balancing tungsten practicals for film,
cooling photo strobes, museum/retail CCT tweaks, and machine-vision setups needing blue-channel gain without
heavy attenuation.
Description
CTB-004 gives tungsten or warm-white LED sources a noticeable cool-up—roughly a ½-CTB step—without wiping out output the way a full CTB film would. Transmittance rises through three distinct peaks— 85 % at 388 nm, ~94 % at 440 nm, and ~93 % at 492 nm. Transmittance never drops below 70 % from the near-UV edge at 380 nm right through to about 513 nm, delivering consistent, high-output energy across the entire violet-to-blue-green band before the curve begins its controlled roll-off. Beyond 515 nm it slopes away, dropping to ~50 % by 525 nm, ~33 % around 550 nm, reaching a low of ~20 % at 700 nm, and edging back up toward ~34 % by 780 nm. The smooth taper prunes red/amber energy enough to lift a 3200 K lamp toward 4300 – 4500 K while preserving plenty of green so skin tones stay natural.
Key advantages
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Mid-strength ½-CTB correction – Raises CCT by roughly 1500–1800 K, ideal for balancing tungsten with cool LED backlights or mild daylight spill.
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High blue-region throughput – ≥ 80 % between 440 – 500 nm keeps fixtures punchy compared with deep-blue gels.
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Progressive red attenuation – Smooth roll-off avoids cyan shifts or green spikes that complicate colour grading.
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Heat-robust oxide stack – All-glass coating survives 1 kW halogen, high-power LED engines, and frequent cleaning.
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Custom formats – Round, square, or free-form parts from 5 mm to 450 mm, 0.21 – 3.8 mm thick, on Borofloat®, soda-lime, Schott D263 T, or Corning Eagle XG glass.
Typical applications
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Stage & architectural lighting – Cool house tungsten rigs to blend with video walls or daylight apertures.
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Film & broadcast – Ease practical lamps a half-step toward daylight so they grade cleanly with HMIs and skylight.
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Photography modifiers – Add a subtle blue lift without stacking multiple gels that cut output.
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Museum & retail displays – Improve colour rendition and whiteness without introducing damaging UV.
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Machine-vision & inspection – Enhance blue-channel contrast for fluorescent brighteners or security inks while maintaining overall brightness.
Need a prototype within days or a production run next month? CTB-004 filters can be coated, cut, and shipped to your exact specification—fast.
